Cooling of liquid in a tube under rotation

Abstract

Good temperature homogenization and cooling time can create a more efficient and sensitive polymerase chain reaction (PCR) process. By using rotation, these can be achieved. This study attempts to understand the velocity and temperature fields inside this PCR-tube for a rotating and non-rotating case during the cooling process.

Through computational fluid dynamics (CFD), the development of the flow in the PCR-tube can be studied in details. It is understood from the previous studies by Martensson et al. (2006) that rotation give rise to flow features that are unique. By comparing the differences in flow field for a rotating and a non-rotating tube with equivalent acceleration in the apex direction, the effect of Coriolis force specifically in affecting the cooling can be analyzed.

In the initial transient state which occurs for only a short duration, the rotating flow field has distinct and unique flow features. Over longer time period, the rotating flow field approaches a similar flow pattern as the non-rotating flow field. Through analyzing the governing equations, this interesting phenomenon is a result of the reducing Coriolis force. In addition, rotating flow field shows better cooling rate than a non-rotating one. However, temperature homogenization remains a problem due to the inherent problem of stratification of the temperature profile.

One possible idea to overcome stratification is to incorporate periodic translational motion into rotation. Due to time constraint, this has not been explore and studied upon.